JP3399239B2 - Power supply - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device.

[0002]

2. Description of the Related Art A first conventional example according to the present invention is shown in FIG.

This circuit includes a rectifier DB for full-wave rectifying the AC power supply Vac, a capacitor C1 connected to the output terminal of the rectifier DB, and a first capacitor connected to both ends of the capacitor C1.
A second field effect transistor (hereinafter referred to as a switching element) Q1 and Q2 connected in series, and a capacitor C connected to both ends of the series connection of the switching elements Q1 and Q2.
2 and the first connected to both ends of the switching element Q2,
The second diode (hereinafter referred to as diode) D1,
A series connection of D2 and an inductance element L1 connected to both ends of the switching element Q1 via a diode D2.
And a smoothing capacitor C3 connected in series, and a coupling capacitor C4 connected to both ends of the switching element Q2.
And a load Z connected in series, and is a power supply device that supplies alternating high-frequency power to the load Z by alternately turning on and off the two switching elements Q1 and Q2. Further, in the circuit including the inductance element L1, the smoothing capacitor C3, and the diodes D1 and D2, the AC power supply Vac is supplied when the switching element Q2 is turned on.
→ Rectifier DB → Inductance element L1 → Smoothing capacitor C3 → Diode D2 → Switching element Q2 → Rectifier DB → Supplying current through the path of AC power supply Vac to charge the smoothing capacitor C3 with a predetermined charging voltage (AC power supply Vac (DC voltage lower than the peak value of) and the output voltage of the rectifier DB becomes lower than the charging voltage of the smoothing capacitor C3, the charging voltage of the smoothing capacitor C3 becomes a half bridge type inverter circuit composed of switching elements Q1, Q2, etc. It becomes a power source. That is, the circuit including the inductance element L1, the smoothing capacitor C3, and the diodes D1 and D2 operates as a so-called partial smoothing power source.

However, in the above-mentioned first conventional example, the following first problem occurs.

When there is no charge in the smoothing capacitor C3 when the power is turned on, the switching element Q2 is turned on, and at the same time, as described above, the AC power source Vac → rectifier DB → inductance element L1 → smoothing capacitor C3 → diode D.
2 → switching element Q2 → rectifier DB → AC power supply Va
The charging current starts flowing through the smoothing capacitor C3 along the path c. Energy is accumulated in the inductance element L1 due to the charging current of the smoothing capacitor C3 flowing when the switching element Q2 is turned on, and when the switching element Q2 is turned off, the energy of the inductance element L1 is changed from the inductance element L1 → the smoothing capacitor C3 → diode. It is emitted in the path of the diode D2 → the built-in diode of the switching element Q1 → the inductance element L1. However, at the initial stage of power-on, since the smoothing capacitor C3 has almost no electric charge, the current value flowing through the inductance element L1 when the switching element Q2 is turned off is large, and the charging voltage of the smoothing capacitor C3 is also low. Therefore, the vibration cycle of the inductance element L1 and the smoothing capacitor C3 becomes very long, that is, the inductance element L1 → the smoothing capacitor C3 → diode.
Inductance element L by the path of D2 → built-in diode of switching element Q1 → inductance element L1
The emission time of 1 energy becomes very long, and therefore
When the switching element Q2 is turned on next time, the current is still flowing through the built-in diode of the switching element Q1. Therefore, during the reverse recovery time of the built-in diode of the switching element Q1, FIG. 8C and FIG.
As shown in the portions A and B of and, switching element Q1
Then, an excessively large short-circuit current is instantaneously generated in the switching element Q2.

As means for solving the above-mentioned first problem,
There is one disclosed in Japanese Patent Application No. 7-254210 filed by the applicant of the present invention, and a circuit diagram thereof is shown in FIG. 9 as a second conventional example according to the present invention.

The difference from the first conventional example shown in FIG. 7 is that it is connected in parallel with the switching element Q2 via a diode D2.
Impedance element (for example, resistor) R1 and third field effect transistor (hereinafter referred to as switching element).
The charging circuit for the smoothing capacitor C3, which is a series connection of Q3, is connected and the switching elements Q1, Q2, Q3 are connected.
This is because the control circuit 1 for driving is provided, and the same configurations as those of the other first conventional example are denoted by the same reference numerals and the description thereof will be omitted.

Next, the operation will be briefly described. When the power is turned on, the switching element Q3 is turned on and the oscillations of the switching elements Q1 and Q2 are stopped, that is, the oscillation of the inverter circuit is stopped. Then, while the switching elements Q1 and Q2 are stopped oscillating, the resistor R1
And a smoothing capacitor C3 via a switching element Q3.
The stored charge is stored in the switching element, the switching element Q3 is turned off, and the switching elements Q1 and Q2 start oscillating.

With this configuration, when the switching elements Q1 and Q2 start to oscillate, the smoothing capacitor C3 is charged with sufficient electric charge, so that the vibration cycle of the inductance element L1 and the smoothing capacitor C3 is increased. Is shortened, and it is possible to prevent the occurrence of excessive current stress on the switching element and the like as described in the first conventional example. Further, since the switching element Q3 is turned off after the oscillation of the switching elements Q1 and Q2 is started, unnecessary power consumption in the resistor R1 does not occur.

The resistor R1 and the switching element Q3
The charging circuit of the smoothing capacitor C3 may include a temperature-dependent resistor such as a thermistor, that is, when the smoothing capacitor C3 is sufficiently charged by self-heating due to the charging current, its resistance value becomes very large. The element may be used.

[0011]

However, the second conventional example has the following second problem.

After the power is turned on, the switching elements Q1 and Q2
When Vac is operating stably, Vac may momentarily drop and recover again, that is, even if a momentary power failure or voltage drop occurs, the control power supply in (1) is sufficiently secured. Therefore, the switching element Q3 continues to be in the off state. Further, since the switching elements Q1 and Q2 continue the oscillating operation, the electric charge of the smoothing capacitor C3 is discharged during the momentary power failure or voltage drop. When the power is restored in this state, the smoothing capacitor C3
Is low and the operation of the charging circuit cannot follow a sharp change in Vac. Therefore, as described in the first conventional example, the switching elements Q1 and Q2 are momentarily excessively large. Short circuit current will occur.

The present invention has been made in view of all the above problems, and an object of the present invention is to provide a power supply device capable of preventing an excessive stress from being applied to a switching element or the like. .

[0014]

In order to solve the above problems, according to the invention of claim 1, a rectifier for rectifying an AC power supply and a first switching element connected in parallel to both ends of the rectifier. And an inverter circuit that includes a series circuit of a second switching element, and supplies an alternating high-frequency voltage to a load by alternately turning on and off the first or second switching element, and a first or second switching element. A partially smoothed power supply that includes a capacitor that is charged by turning on one of them, and that partially smooths the DC voltage output of the rectifier to be the power supply for the inverter circuit, and a charging circuit that starts charging the capacitor before the oscillation of the inverter circuit starts. When the voltage across the capacitor drops below a certain value during the oscillation operation of the inverter circuit, the oscillation of the inverter circuit is stopped and By operating the charging circuit, characterized in that a control circuit for charging the capacitor.

According to the second aspect of the invention, the rectifier for rectifying the AC power source, the first switching element having one end connected to the high voltage side of the rectifier and the second switching element having one end connected to the low voltage side of the rectifier. An inverter circuit including a series circuit of switching elements, a first switching element and a second switching element
A control circuit for driving the switching element, a series circuit including a capacitor and an inductance element, one end of which is connected to a high voltage side terminal of the first switching element;
A second diode in which a cathode terminal is connected to a low-voltage side terminal of the switching element and an anode terminal is connected to the other end of a series circuit including a capacitor and an inductance element, and a second switching element via the second diode Before the start of oscillation of the first and second switching, comprising a series circuit of a first diode connected in parallel in the opposite direction to the first diode and an impedance element and a third switching element connected in parallel to the first diode. And a load connected in parallel to the second switching, and the control circuit is configured so that the voltage across the capacitor is equal to or less than a certain value during the oscillating operation of the first and second switching elements. Then, the oscillation of the first and second switching elements is stopped and the third switching element is turned on to charge the capacitor. Characterized in that it is intended to.

According to the third aspect of the invention, the direction in which the input current from the DC output terminal of the rectifier flows between the DC output terminal of the rectifier and the contacts of the load and the low-voltage side terminal of the second switching element. Is connected to a third diode, and a fourth diode is connected to both ends of the second switching element through a load and in a direction in which an input current from the DC output terminal of the rectifier flows. It is characterized in that an impedance element is connected in parallel with.

According to the invention described in claim 4, by detecting the overcurrent flowing through at least one of the first and second switching elements and outputting a signal to the control circuit,
It is characterized in that a current detection circuit for stopping the oscillation of the first and second switching elements and operating the charging circuit to charge the capacitor is provided.

According to the invention described in claim 5, by detecting the voltage drop of the AC power source and outputting a signal to the control circuit, the oscillation of the inverter circuit is stopped and the charging circuit is operated to charge the capacitor. A power supply detection circuit is provided.

According to the sixth aspect of the present invention, the charging circuit gradually charges at least the capacitor to a certain voltage value when the voltage across the capacitor becomes a certain value or less during the oscillation operation of the inverter circuit. And

According to a seventh aspect of the invention, the first to third switching elements are field effect transistors.

According to an eighth aspect of the present invention, the load includes a discharge lamp.

..

[Embodiment]

(Embodiment 1) FIG. 1 shows a circuit diagram of a first embodiment according to the present invention.

The difference from the second conventional example shown in FIG. 9 is that the resistor R2 connected between the source terminal of the switching element Q2 and the negative output terminal of the rectifier DB and the contact points of the switching element Q2 and the resistor R2. A diode D3 having an anode terminal connected to the capacitor C5, a capacitor C5 connected in parallel to both ends of the resistor R2 via the diode D3, and a capacitor C
A resistor R3 and a capacitor C5 connected in parallel at both ends of
The control circuit 1 compares the voltage across both terminals and the reference voltage VREF.
Is provided with a comparator Comp1 that outputs a signal to the output terminal, and a current detection circuit that detects the current flowing through the switching element Q2 is provided. By assigning the same reference numerals to the same configurations as the other second conventional examples, The description is omitted. The control circuit 1 controls the switching elements Q1, Q2, Q3 so that when the output of the comparator Comp1 becomes high level, the oscillating operation of the switching elements Q1, Q2 is stopped and the switching element Q3 is turned on. To do.

Next, the operation will be briefly described. In the present embodiment, when the switching elements Q1 and Q2 are operating stably, a momentary power failure or voltage drop of the AC power supply Vac occurs, and when an overcurrent flows through the switching element Q2 when the power is restored, the diode D3 is generated. A voltage is generated across the capacitor C5 via. When the voltage across the capacitor C5 exceeds the reference voltage VREF, the comparator Comp1
Becomes high level, the control circuit 1 receives the output and stops the oscillating operation of the switching elements Q1 and Q2, and turns on the switching element Q3. When the switching element Q3 is turned on, the smoothing capacitor C3 is charged as described in the second conventional example. Therefore, when a momentary power failure or a voltage drop occurs, the switching elements Q1 and Q3
It is possible to prevent a momentary excessive short-circuit current from being generated.

(Second Embodiment) FIG. 2 shows a circuit diagram of a second embodiment according to the present invention, and FIG. 3 shows an operation waveform diagram thereof.

The difference from the first embodiment shown in FIG. 1 is that the reference voltage VRE is applied to the positive input terminal of the comparator Comp1.
F, the voltage across the capacitor C5 is input to the negative input terminal, the capacitor C6 connected between the output terminal of the comparator Comp1 and the ground, and the control power supply Vc.
c and the resistor R4 connected between the output terminals of the comparator Comp1, the voltage across the capacitor C6 and the reference voltage VRE
Comparator Com that compares F and outputs a signal to the control circuit 1
Since the timer circuit composed of p2 is provided, the same configurations as those of the other first embodiment are denoted by the same reference numerals and the description thereof will be omitted. In the circuit shown in FIG. 2, the AC power supply Vac shown in FIG. 1, the rectifier DB, the capacitors C1 and C2, the coupling capacitor C4, the smoothing capacitor C3, the inductance element L1, the diodes D1 and D2, the switching elements Q1 and Q3, and the resistors. R1,
The load Z is not shown.

Next, the operation will be briefly described with reference to FIG. In the present embodiment, when the switching elements Q1 and Q2 are operating stably, a momentary power failure or voltage drop of the AC power supply Vac occurs, and when an overcurrent flows through the switching element Q2 when the power is restored, the diode D3 is generated. A voltage is generated across the capacitor C5 via. And FIG.
As shown in (b), when the voltage across the capacitor C5 exceeds the reference voltage VREF1, the output of the comparator Comp1 becomes low level. Then, the charge stored in the capacitor C6 is discharged through the output of the comparator Comp1, and at that moment, the output of the comparator Comp2 becomes low level. The control circuit 1 receives the output and switches Q1,
Q2 is stopped and the switching element Q3 is turned on as shown in FIG. When the switching element Q2 is turned off, the charge charged in the capacitor C5 is discharged through the resistor R3. Then, when the voltage across the capacitor C5 falls below the reference voltage VREF1, the output of the comparator Comp1 becomes high level, and the capacitor C6 is gradually charged via the resistor R4. As shown in FIG. 3C, the capacitor C6
When the voltage across both terminals of the comparator Comp2 exceeds the reference voltage VREF2, the switching elements Q1 and Q2
2 starts oscillating, and the switching element Q3 turns off as shown in FIG. That is, when an overcurrent flows through the switching element Q2 even for one pulse, the oscillating operation of the switching elements Q1 and Q2 is stopped and the switching element Q3 is turned on, so that the smoothing capacitor C3 is activated as described in the second conventional example. The timer time is set by the resistor R4 and the capacitor C6 so that the charging is performed and the charging is sufficiently performed.

Therefore, it is possible to prevent an instantaneously excessive short-circuit current from being generated in the switching elements Q1 and Q2 when an instantaneous power failure or voltage drop occurs.

(Third Embodiment) FIG. 4 shows a circuit diagram of a third embodiment according to the present invention.

The difference from the first embodiment shown in FIG. 1 is that, instead of the current detection circuit for detecting the current flowing in the switching element Q2, a rectifier DB2 connected to both ends of the AC power supply Vac and a rectifier DB2. A capacitor C7 connected in parallel between the DC output terminals of, and a series connection of a resistor R5 and a resistor R6 connected in parallel at both ends of the capacitor C7,
The comparator Comp1 that compares the voltage V1 (hereinafter, referred to as voltage V1) obtained by dividing the voltage across the capacitor C7 by the resistors R5 and R6 with the reference voltage VREF and outputs a signal to the control circuit 1 That is, a power supply detection circuit for detecting an instantaneous change of the AC power supply Vac is provided, and the same reference numerals are given to the same configurations as those of the other first embodiment, and the description thereof will be omitted. In addition, the comparator Com
The reference voltage VREF is input to the positive input terminal of p1 and the voltage V1 is input to the negative input terminal.

Next, the operation will be briefly described. In the present embodiment, when the switching elements Q1 and Q2 are operating stably, if a momentary power failure or a voltage drop occurs in the AC power supply Vac, the voltage V1 drops accordingly and falls below the reference voltage VREF. , The output of the comparator Comp1 becomes high level, the control circuit 1 receives the output and stops the switching elements Q1 and Q2, and the switching element Q3.
Turn on. When the switching element Q3 is turned on, the smoothing capacitor C3 is charged as described in the second conventional example. Therefore, when a momentary power failure or voltage drop occurs, the switching elements Q1 and Q2 are momentarily excessively short-circuited. It is possible to prevent an electric current from being generated. In addition, the comparator Com
The input signal to the negative input terminal of p1 may be obtained from the voltage across capacitor C1.

(Fourth Embodiment) FIG. 5 shows a circuit diagram of a fourth embodiment according to the present invention.

The difference from the first embodiment shown in FIG. 1 is that a smoothing capacitor C3 and a diode D1 are connected to both ends of a series circuit instead of the current detecting circuit for detecting the current flowing in the switching element Q2. A series connection of the resistors R7 and R8 is compared with a reference voltage VREF, which is a voltage V2 (hereinafter referred to as voltage V2) obtained by dividing the voltage across the series circuit of the smoothing capacitor C3 and the diode D1 by the resistors R7 and R8. And a smoothing capacitor C3 including a comparator Comp1 that outputs a signal to the control circuit 1.
The voltage detection circuit for detecting the voltage change is provided, and the same configurations as those of the other first embodiment are denoted by the same reference numerals and the description thereof will be omitted. In addition, the comparator Com
The reference voltage VREF is input to the positive input terminal of p1 and the voltage V2 is input to the negative input terminal.

Next, the operation will be briefly described. In the present embodiment, when the switching elements Q1 and Q2 are operating stably, if a momentary power failure or a voltage drop occurs in the AC power supply Vac, the charging charge of the smoothing capacitor C3 is equal to the inductance element L1 and the diode D1. As a result, the voltage across the smoothing capacitor C3 drops. At this time, since the diode D1 is in the ON state,
The resistors R7 and R8 are in a state of detecting the voltage across the smoothing capacitor C3. When the voltage across the smoothing capacitor C3 becomes equal to or lower than a predetermined value, the voltage V2 falls below the reference voltage VREF accordingly, so that the output of the comparator Comp1 becomes high level, and the control circuit 1 receives the output and the switching elements Q1, Q2. Stop the switching element Q
Turn on 3. As the switching element Q3 is turned on, the smoothing capacitor C3 is turned on as described in the second conventional example.
Therefore, it is possible to prevent an instantaneously excessive short-circuit current from being generated in the switching elements Q1 and Q2 when an instantaneous power failure or voltage drop occurs. It should be noted that the comparator Com is provided with the timer circuit as shown in the second embodiment.
The output of p1 causes the switching elements Q1,
You may comprise so that Q2 may turn off and switching element Q3 may turn on.

In all of the above embodiments, the switching element Q3 may be a mechanical switch such as a relay, and may be any element that charges the smoothing capacitor C3 before the oscillation of the switching elements Q1 and Q2 is started. Anything is fine.
Further, in all of the above-mentioned embodiments, the half-bridge type inverter circuit including the switching elements Q1 and Q2 is used. However, other than the two-stone type, another one-type or four-type type inverter circuit is used. May be. Furthermore, although the switching elements Q1 to Q3 are step-effect transistor transistors, they may be bipolar transistors and diodes connected in anti-parallel thereto.
The load Z may be a discharge lamp.

In all the above-mentioned embodiments, FIG.
As shown in, a third diode (hereinafter, referred to as a diode) D4 having a cathode terminal connected to the negative output terminal of the rectifier DB and an anode terminal connected to one end of the load Z.
A fourth diode (hereinafter, referred to as a diode) D5 that connects a cathode terminal to the contact point of the diode D4 and the load Z and an anode terminal to the source terminal of the switching element Q2, and is connected in parallel to both ends of the diode D5. The impedance element 2 may be provided. With such a configuration, the input current can flow even near the zero cross of the AC power supply Vac, that is, the input current distortion can be improved.

[0037]

According to the first, second, and fourth to seventh aspects of the present invention, the switching element and the like are excessively large, including the case where a momentary power failure or a voltage drop occurs in the AC power supply. It is possible to provide a power supply device capable of preventing application of various stresses.

According to the third aspect of the present invention, the input current distortion can be improved, and excessive stress is applied to the switching element, including the case where a momentary power failure of the AC power source or a voltage drop occurs. It is possible to provide a power supply device capable of preventing such a situation.

According to the eighth aspect of the present invention, the discharge lamp can be stably lit, and excessive stress is applied to the switching element, including the case where a momentary power failure or voltage drop of the AC power source occurs. It is possible to provide a power supply device capable of preventing such a situation.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment according to the present invention.

FIG. 2 is a circuit diagram showing a second embodiment according to the present invention.

FIG. 3 is an operation waveform diagram according to the above embodiment.

FIG. 4 is a circuit diagram showing a third embodiment according to the present invention.

FIG. 5 is a circuit diagram showing a fourth embodiment according to the present invention.

FIG. 6 is a circuit diagram showing another inverter circuit configuration according to the first to fourth embodiments.

FIG. 7 is a circuit diagram showing a first conventional example according to the present invention.

FIG. 8 is an operation waveform diagram according to the conventional example.

FIG. 9 is a circuit diagram showing a second conventional example according to the present invention.

[Explanation of symbols]

C capacitor D diode DB rectifier L inductance element Q switching element R resistance Vac AC power supply Z load 1 control circuit 2 Impedance element

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02M 7/48 H02H 7/122 H02M 7/538 H05B 41/24

Claims (8)

(57) [Claims] 1. A rectifier for rectifying an AC power supply, and a series circuit of a first switching element and a second switching element connected in parallel at both ends of the rectifier, and the first or second switching element. An inverter circuit that supplies an alternating high-frequency voltage to a load by alternately turning on and off switching elements, and a capacitor charged by turning on one of the first and second switching elements, and a DC voltage output of the rectifier. In a power supply device comprising a partially smoothed power source for partially smoothing the power source of the inverter circuit and a charging circuit for starting charging of the capacitor before the oscillation of the inverter circuit, the oscillation of the inverter circuit When the voltage across the capacitor during operation falls below a certain value, the oscillation of the inverter circuit is stopped, and Power supply, characterized in that serial by operating the charging circuit provided with a control circuit for charging the capacitor. 2. A series circuit of a rectifier for rectifying an AC power source, a first switching element whose one end is connected to the high voltage side of the rectifier and a second switching element whose one end is connected to the low voltage side of the rectifier. An inverter circuit including; a control circuit for driving the first switching element and the second switching element; and a capacitor and an inductance element whose one end is connected to a high voltage side terminal of the first switching element. And a second diode having a cathode terminal connected to the low-voltage side terminal of the first switching element and an anode terminal connected to the other end of the series circuit including the capacitor and the inductance element, The second via the second diode
A first diode that is reversely connected in parallel to the switching element and a parallel connection to the first diode,
A charging circuit which comprises a series circuit of an impedance element and a third switching element, and which starts charging of the capacitor before the oscillation of the first and second switching is started;
In a power supply device comprising a load connected in parallel to the second switching, the control circuit, when the voltage across the capacitor becomes a certain value or less during oscillating operation of the first and second switching elements, A power supply device, which stops oscillation of the first and second switching elements and turns on the third switching element to charge the capacitor. 3. The third rectifier between the DC output terminal of the rectifier and the contacts of the load and the low-voltage side terminal of the second switching element, and in a direction in which an input current from the DC output terminal of the rectifier flows. A fourth diode connected to the second switching element across the load and in a direction in which an input current from the DC output terminal of the rectifier flows.
3. The power supply device according to claim 2, wherein the diode is connected, and an impedance element is connected in parallel to both ends of the fourth diode. 4. The oscillation of the first and second switching elements is stopped by detecting an overcurrent flowing in at least one of the first and second switching elements and outputting a signal to the control circuit. In addition to the above, a current detection circuit for operating the charging circuit to charge the capacitor is provided.
The power supply device according to. 5. A power supply detection device that detects a voltage drop of the AC power supply and outputs a signal to the control circuit to stop oscillation of the inverter circuit and operate the charging circuit to charge the capacitor. The power supply device according to claim 1 or 2, further comprising a circuit. 6. The charging circuit gradually charges at least the capacitor to a certain voltage value when the voltage across the capacitor becomes a certain value or less during the oscillation operation of the inverter circuit. 1 to claim 5
The power supply device according to any one of 1. 7. The power supply device according to claim 1, wherein the first to third switching elements are field effect transistors. 8. The power supply device according to claim 1, wherein the load includes a discharge lamp.